Electric fuel pump control circuit for intermittent injection electronic fuel control systems

ABSTRACT

A fuel pump control circuit is disclosed herein to provide optimum fuel delivery at constant operating pressure to the fuel injector valve means of an electronically controlled fuel supply system. By energizing the pump in response to the engine operating parameters which determine the engine fuel requirement, a minimum of fuel in excess of the fuel requirement is recirculated from the area of the engine back to the fuel reservoir. In order to suitably energize the fuel pump, the pump is provided with a maximum voltage during the time period of the injection pulse with the energizing voltage decreasing thereafter so that a minimum of fuel is circulated through the fuel supply system during the noninjection phase. This provides a variable level of average fuel pump energization.

United States Patent Reddy 1 51 July 9, 1574 1 ELECTRIC FUEL PUMP CONTROL 3,587,545 6/1971 Ballou 123/136 CIRCUIT FOR INTERMI'ITENT INJECTION 3,643,635 2/1972 Milam 123/32 EA 3,669,081 6/1972 Monpetit 123/32 EA ELECTRONIC FUEL CONTROL SYSTEMS [75] Inventor: Junuthula N. Reddy, Horseheads,

[73] Assignee: The Bendix Corporation, Southfield,

Mich.

[22] Filed: June 30, 1971 [21] Appl. No.: 158,351

[52] U.S. Cl. 123/32 EA, 123/139 E [51] Int. Cl. F02m 51/00 [58] Field of Search 123/32 AB, 32 EA, 119, 123/136, 139 E, 139 AW, 140 MP [56] References Cited UNITED STATES PATENTS 2,981,246 4/1961 Woodward 123/32 EA 3,036,564 5/1962 Guiot 123/32 EA 3,236,221 2/1966 Lear 1. 123/136 3,319,613 5/1967 Begley et a1 123/32 EA 3,429,302 2/1969 Scholl 123/32 EA 3,470,854 10/1969 Eiscle et a1. 123/32 EA TEMPERATURE SENSOR BATTERY Primary ExaminerLaurence M. Goodridge Assistant Examiner-Cort Flint Attorney, Agent, or Firm-R. A. Benziger; R, J. Eifler ABSTRACT A fuel pump control circuit is disclosed herein to provide optimum fuel delivery at constant operating pressure to the fuel injector valve means of an electronically controlled fuel supply system, By energizing the pump in response to the engine operating parameters which determine the engine fuel requirement, a minimum of fuel in excess of the fuel requirement is recirculated from the area of the engine back to the fuel reservoir. In order to suitably energize the fuel pump, the pump is provided with a maximum voltage during the time period of the injection pulse with the energizing voltage decreasing thereafter so that a minimum of fuel is circulated through the fuel supply system during the noninjection phase. This provides a variable level of average fuel pump energization.

8 Claims, 3 Drawing Figures FUEL PUMP CONTROL ELECTRONIC Tl MlNu CONTROL 10 PICKUP UNIT PATENTEDJUL 91914 SHEEI 1 [IF 2 FUEL PUMP CONTROL SENSOR BATTERY TEMPERATURE ELECTRONIC CONTROL UNIT- TIMING PICKUP FIGURE JUNUTHULA N. REDDY INVENTOR.

mammm 91914 3.822.677

SHEEI 2 0F 2 FIGURE 2 TRIGGER DURATION FIGURE 3 JUNUTHULA N. REDDY INVENTOR.

ELECTRIC FUEL PUMP CONTROL CIRCUIT FOR INTERMITTENT INJECTION ELECTRONIC FUEL v CONTROL SYSTEMS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the field of electronic fuel control systems for internal combustion engines. More particularly, the present invention relates to that portion of the above noted field which is con cerned with a control of the fuel supply pumping means.

2. Description of the Prior Art In fuel control systems which provide fuel to reciprocating piston internal combustion engines on an intermittent, or pulse, basis the prior art teaches that the fuel pumps per se are to be energized by a substantially constant level voltage so as to provide fuel to the fuel injector valve means at a fixed, constant pressure and flow rate commensurate with maximum requirements. Typically, these systems provide accumulator means to assist stabilizing fuel pressure, with return lines being supplied to return to the fuel reservoir fuel quantities in excess of that required by the engine. In such systems, it is known that fuel which is recirculated to the vehicle fuel reservoir will contain large amounts of heat which have been picked up from the engine compartment of the vehicle. Such systems usually provide elaborate mechanisms within the fuel tanks to separate the heated fuel from the fuel residing in the reservoir at ambient air temperature so as to prevent percolation loss of vapor and general increase in the fuel temperature within the fuel tank. One difficulty with an elevated temperature in the fuel reservoir is that hydrocarbon emissions are generated to pollute the atmosphere. An additional problem, of course, is the fact that lost fuel vapors decrease vehicle efficiency and mileage. A further problem with the recycling of heated fuel back to the fuel reservoir is the fact that vapor lock situations can occur when heated fuel is drawn into the pump intake and this fuel subsequently vaporizes. It is, therefore, an object of the present invention to provide a control circuit for the fuel pump of such electronic fuel control systems as will permit that pump to operate at an average energization to provide the desired fuel flow and pressure rates when necessary for the injection of fuel but which will otherwise permit the pump to operate at reduced fuel flow rates to decrease the heat contamination of the fuel in the fuel reservoir.

A proposed solution to this problem as contained in co-pending commonly assigned patent application docket No. MOC 70/40 has been to pulse the fuel pump in synchronism with the provision of the injector operating pulses. However, I have found that such a system suffers from the response time lag of mechanical devices such as fuel pumps when combined with the long line attenuation which occurs between the fuel supply and the fuel injection points. Accordingly, it is a still further object of my invention to provide a fuel pump control circuit which permits the fuel pump to maintain a low quantity, high pressure of fuel circulation at the necessary injection pressure and whose energization level is increased in substantial synchronization with the injection pulses to thereby increase the quantity flow of fuel so that, during the injection periods, suitable quantities of fuel at sufficient pressure are available for injection. It is a still further object of the present invention to provide a means for variably energizing a pumping means having an output characteristic which is proportional to average energization level wherein the average energization of the pump is increased to provide increased quantity flow.

SUMMARY OF THE INVENTION The present invention contemplates a circuit adapted to receive the fuel injection command pulses and, in response thereto, to produce an output voltage having a maximized value. Upon termination of the injection control pulse, an electrical energy storage means is discharged in a constant discharge pattern so as to reduce the output voltage towards a minimal value. This circuit is adapted at its output to power the fuel pumping means situated within the fuel supply system of an internal combustion engine. By applying the output voltage signal to a fluid pumping means in which the quan tity of fluid pumped is a direct function of the excitation voltage, the pump output may be modulated to more closely resemble the fuel requirements of the associated internal combustion engine.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates an internal combustion engine fuel control system that incorporates the fuel pump control means of the present invention.

FIG. 2 illustrates a preferred embodiment of the fuel pump control means of FIG. 1.

FIG. 3 illustrates a voltage output curve with respect to time for the circuit of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, an electronic fuel control system incorporating the fuel pump control of the pres ent invention is illustrated in schematic form. The system is comprised of a computing means 10, a manifold pressure sensor 12, a temperature sensor 14, an input timing means 16, and various other parameter sensors denoted as 18. The manifold pressure sensor 12 and the associated other sensors 18 are mounted on throttle body 20. The output of the computing means 10 is coupled to an electromagnetic injector valve member 22 mounted in intake manifold 24 and arranged to provide fuel from fuel tank 26 via pumping means 28 and suitable fuel conduits 30 to a combustion chamber 32 of an internal combustion engine not otherwise shown. While the injector valve member 22 is illustrated as delivering aspray of fuel towards an open intake valve 34, it will be understood that this representation is merely illustrative and that other delivery arrangements are known and utilized. Furthermore, it is well known in the art of electronic fuel control systems that computing means 10 may control an injector valve means comprised of one or more injector valve members 22 arranged to be actuated singly or in groups of varying numbers and in a sequential fashion as well as simultaneously. The computing means 10 is shown here as energized by battery 36 which could be a vehicle battery and/or vehicle battery charging system or a separate auxiliary battery.

Fuel pumping means 28 is shown in FIG. 1 as being controlled by fuel pump control 38 which receives an input signal from the electronic computing unit 10. The signal received by fuel pump control 38 may be, for instance, the same signal as provided to injector valve means 22. In those systems where a plurality of injector valve means are sequentially energized, either singly or in groups, to provide the total fuel requirement for the internal combustion engine, the fuel pump control 38 may receive as input each computing means output signal either from a common location within the computing means if such is available, or by suitably adapted input coupling from each of the injector valve means 22 which are sequentially energized.

Referring now to FIG. 2, the fuel pump control 38 of FIG. I is illustrated in a preferred electrical schematic. The circuit comprises input transistor 40, electrical energy storage means 42 in the form of a capacitor, output means 44, electrical energy discharge control transistor 46, and dissipating resistor 47. The base of transistor 46 is connected to ground via constant voltage drop means 48 in the form of a plurality of diodes and is also connected to the B+ source of electrical supply by way of resistor 50. Resistor 50 and voltage drop means 48 are cooperative to provide, at the base of transistor 46, a fixed voltage potential. This fixed voltage will maintain transistor 46 in a state of conduction so as to pass a fixed current through resistor 47. This will draw energy off of the energy storage means 42 at a fixed rate whenever transistor 40 is nonconductive.

Output transistor means 44 are comprised of a first transistor 52 which operates as a signal amplification device and a second transistor 54 which operates as a power transistor. In the event that a suitable power transistor having the necessary signal amplification capabilities is available for the particular application intended, output transistor means 44 may comprise only one transistor. The emitter of power transistor 54 pro vides the output signal through output terminal V The voltage appearing at this output terminal corresponds to the voltage across energy storage means 42 less the emitter base voltage drops of transistors 52 and 54.

The base of transistor 40 is coupled through input resistance 56, input diode 58 and input terminal 60 to a suitable source of triggering pulses within the electronic control unit 10. In those systems where injection of all cylinders takes place substantially simultaneously, this input may be for instance at one of the injector valve means or, in systems where the injector valves are energized in a sequential fashion, input terminal 60 may be connected to the portion of the electronic control unit wherein the injection pulse width is computed. In those systems where a plurality of injector valve means are sequentially energized, an alternative arrangement would place a plurality of diodes in parallel, with the cathode of each connected to a suitable injector valve means 22 and the anode of each connected to input resistance 56. Load resistance 62 is coupled between the emitter of transistor 40 and the source ofelectrical energy B+. The output terminal V may be connected to any suitable fluid pumping means whose flow capacity is proportional to the amount of energizing signal.

OPERATION Upon receipt of a triggering signal at input terminal 60, which signal should, in this embodiment, be the appearance of a ground or common low potential at terminal 60, transistor 40 will begin to conduct and energy will flow into energy storage means 42 at a relatively rapid fashion charging capacitor 42 up to substantially the 8+ value. Transistor 46 will be biased on and will be conducting current therethrough. Upon termination of the trigger signal at terminal 60, transistor 40 will be switched off and the voltage across capacitor 42 will begin to decrease due to the conduction of energy away from energy storage means 42 by transistor 46. The voltage appearing across capacitor 42 will be communicated via the emitter-base junction of transistor 52 and the emitter-base junction of transistor 54 to the output terminal V Referring now to FIG. 3, a graph of output voltage with respect to time is illustrated. The voltage graphed is that appearing at output terminal V of FIG. 2. Also illustrated in the FIG. 3 graph is a curve representative of the triggering frequency. The time period denoted as 1 trigger duration corresponds to the time required for one complete engine cycle divided by the total number of discrete injections which must occur during that time period. Also denoted on the vertical axis of the graph is the value which would represent the 8+ voltage and a second value denoted as V During the time interval from T equal to O to I an injection pulse has been generated by the electronic control unit 10 and the suitable pulse has been received at terminal 60. As described hereinabove, capacitor 42 has been charged up to a value which is close to the B+ value and this value remains constant during the time interval of receipt of the injection command at terminal 60. At t,, the injection command terminates, and the energy appearing across energy storage means 42 begins to deteriorate due to the current draw action of transistor 46. This causes the voltage appearing at output terminal V to linearly decrease from the maximum constant level down to the value denoted as V,. This value is a function of the rate at which transistor 46 draws energy from energy storage means 42 and also the time interval from t, to Time t then corresponds to the next triggering cycle of the vehicle engine. As will be observed, the average voltage appearing at output terminal V and therefore the average energization available to drive the fuel pumping means 28 will increase with increasing pulse width (pulse width from time T O to time t,) and also with increasing engine rpm which could correspond to a decrease in the time interval from O to Thus, in both situations where increased fuel delivery to the engine is necessary, the fuel pumping means 28 will be receiving electrical energy in excess of that normally received and will therefore be pumping at a greater average capacity to satisfy the needs of the associated engine.

It will be observed that the present invention accomplishes its stated objectives. However, the embodiment presented hereinabove should be recognized as exemplary and that various modifications, changes, and variations may be made without departing from the spirit of the invention. For example, the various electronic devices illustrated, the electrical polarity and the type of energy storage device may be readily changed by the man of ordinary skill in the art.

I claim:

1. A fuel pump control circuit for an internal combustion engine fuel control system having pulse generating means for producing pulses having durations indicative of the fuel requirement, injector valve means responsive to said pulses for supplying fuel to the engine, and energizable fuel pump means having an average flow capacity proportional to average energization, said fuel pump control circuit comprising:

output means for providing a variable level fuel pump energizing signal; and

control means responsive to the pulse generating means operative to energize the output means to a maximum value during receipt of a pulse and to gradually reduce the energization during the entire interval between successive pulses whereby the average energization is proportional to the output pulse duration and inversely proportional to the interval between successive output pulses.

2. A fuel pump control circuit for an internal combustion engine fuel control system having pulse generating means for producing pulses having durations indicative of the fuel requirement, injector valve means responsive to said pulses for supplying fuel to the engine, and energizable fuel pump means having an average flow capacity proportional to average energization, said fuel pump control circuit comprising:

output means for providing a variable level fuel pump energizing signal; and

control means responsive to the pulse generating means operative to energize the output means to a maximum value during receipt of a pulse and to gradually reduce the energization during the interval between successive pulses whereby the average energization is proportional to the output pulse duration and inversely proportional to the interval between successive output pulses, wherein said control means comprise:

pulse receiving input means;

first switching control means for providing a maximum energizing signal to said output means during receipt of a pulse;

electrical energy storage means for accumulating energy during receipt of a pulse;

means electrically connecting said storage means to energize said output means; and

energy draining means connected to said energy storage means operative to dissipate the energy stored therein and thereby gradually reduce energization of said output means during intervals between successive pulses 3. The system as claimed in claim 2 wherein said storage means comprise a capacitor and said draining means comprise a current sink.

4. A fuel supply system for internal combustion engines comprising:

a fuel supply means;

computing means operative to generate an output pulse signal having a duration representative of the engine fuel requirement; injector valve means responsive to said computing means signal to be actuated for a period of time determined by said signal pulse duration;

energizable fuel pumping means associated with said fuel supply means operative to provide fuel under pressure to said injector valve means whereby said pressurized fuel will be provided to the engine during the period of actuation of said injector valve means;

said fuel pumping means having a flow capacity substantially proportional to the energization thereof; and

fuel pump control means responsive to the computing means output signal duration and further responsive to the interval between successive output pulses operative to energize said fuel pump to a maximum value during a pulse and to gradually reduce fuel pump energization during the entire in- 5 terval between successive pulses.

5. A fuel supply system for internal combustion engines comprising:

a fuel supply means;

computing means operative to generate an output pulse signal having a duration representative of the engine fuel requirements; injector valve means responsive to said computing means signal to be actuated for a period of time determined by said signal pulse duration;

energizable fuel pumping means associated with said fuel supply means operative to provide fuel under pressure to said injector valve means whereby said pressurized fuel will be provided to the engine during the period of actuation of said injector valve means;

said fuel pumping means having a flow capacity substantially proportional to the energization thereof; and

fuel pump control means responsive to the computing means output signal duration and further responsive to the interval between successive output pulses operative to energize said fuel pump to a maximum value during a pulse and to gradually reduce fuel pump energization during an interval between succesisve pulses, wherein said fuel pump control means comprises:

input means;

electrical energy storage means responsive input means to store electrical energy;

said input means adapted to receive the computing means output pulses and operative to cause said storage means to accumulate a maximum stored value during receipt of the computing means output pulses;

energy draining means connected to said energy storage means operative to dissipate the energy stored therein; and

pump output means connected to said energy storage means and said energy draining means operative to communicate the instantaneous energy level appearing at said storage means to the pump.

6. The fuel supply system as claimed in claim 5 wherein said storage means comprise a capacitor and said draining means comprise a current sink.

7. The fuel pump control circuit as claimed in claim 1 wherein said fuel pump control comprises:

input means;

electrical energy storage means responsive to said input means to store electrical energy; said input means adapted to receive the computing means output pulses and operative to cause said storage means to accumulate a maximum stored value during the receipt of the computing means output pulses;

energy draining means connected to said energy storage means operative to dissipate the energy stored therein; and

pump output means connected to said energy storage means and said energy draining means operative to communicate the instantaneous energy level appearing at said storage means to the pump.

to said 8. The fuel supply means as claimed in claim 4 energy draining means connected to said energy stor- Wnereln fuel P p control Ynwns COmPr'Se$? age means operative to dissipate the energy stored electrical energy storage means responsive to said therein. and

input means to store electrical energy;

said input means adapted to receive the computing 5 ns and Sade r drainin means 0 erative to means output pulses and operative to cause said mea gy g P storage means to accumulate a maximum stored Communicate the instantaneous energy level P value during receipt of the computing means outp g at Said g6 e ns to t e pump. put pulses;

pump output means connected to said energy storage 

1. A fuel pump control circuit for an internal combustion engine fuel control system having pulse generating means for producing pulses having durations indicative of the fuel requirement, injector valve means responsive to said pulses for supplying fuel to the engine, and energizable fuel pump means having an average flow capacity proportional to average energization, said fuel pump control circuit comprising: output means for providing a variable level fuel pump energizing signal; and control means responsive to the pulse generating means operative to energize the output means to a maximum value during receipt of a pulse and to gradually reduce the energization during the entire interval between successive pulses whereby the average energization is proportional to the output pulse duration and inversely proportional to the interval between successive output pulses.
 2. A fuel pump control circuit for an internal combustion engine fuel control system having pulse generating means for producing pulses having durations indicative of the fuel requirement, injector valvE means responsive to said pulses for supplying fuel to the engine, and energizable fuel pump means having an average flow capacity proportional to average energization, said fuel pump control circuit comprising: output means for providing a variable level fuel pump energizing signal; and control means responsive to the pulse generating means operative to energize the output means to a maximum value during receipt of a pulse and to gradually reduce the energization during the interval between successive pulses whereby the average energization is proportional to the output pulse duration and inversely proportional to the interval between successive output pulses, wherein said control means comprise: pulse receiving input means; first switching control means for providing a maximum energizing signal to said output means during receipt of a pulse; electrical energy storage means for accumulating energy during receipt of a pulse; means electrically connecting said storage means to energize said output means; and energy draining means connected to said energy storage means operative to dissipate the energy stored therein and thereby gradually reduce energization of said output means during intervals between successive pulses.
 3. The system as claimed in claim 2 wherein said storage means comprise a capacitor and said draining means comprise a current sink.
 4. A fuel supply system for internal combustion engines comprising: a fuel supply means; computing means operative to generate an output pulse signal having a duration representative of the engine fuel requirement; injector valve means responsive to said computing means signal to be actuated for a period of time determined by said signal pulse duration; energizable fuel pumping means associated with said fuel supply means operative to provide fuel under pressure to said injector valve means whereby said pressurized fuel will be provided to the engine during the period of actuation of said injector valve means; said fuel pumping means having a flow capacity substantially proportional to the energization thereof; and fuel pump control means responsive to the computing means output signal duration and further responsive to the interval between successive output pulses operative to energize said fuel pump to a maximum value during a pulse and to gradually reduce fuel pump energization during the entire interval between successive pulses.
 5. A fuel supply system for internal combustion engines comprising: a fuel supply means; computing means operative to generate an output pulse signal having a duration representative of the engine fuel requirements; injector valve means responsive to said computing means signal to be actuated for a period of time determined by said signal pulse duration; energizable fuel pumping means associated with said fuel supply means operative to provide fuel under pressure to said injector valve means whereby said pressurized fuel will be provided to the engine during the period of actuation of said injector valve means; said fuel pumping means having a flow capacity substantially proportional to the energization thereof; and fuel pump control means responsive to the computing means output signal duration and further responsive to the interval between successive output pulses operative to energize said fuel pump to a maximum value during a pulse and to gradually reduce fuel pump energization during an interval between succesisve pulses, wherein said fuel pump control means comprises: input means; electrical energy storage means responsive to said input means to store electrical energy; said input means adapted to receive the computing means output pulses and operative to cause said storage means to accumulate a maximum stored value during receipt of the computing means output pulses; energy draining means connected to said energy storage means operative to dissipate the energy stored therein; And pump output means connected to said energy storage means and said energy draining means operative to communicate the instantaneous energy level appearing at said storage means to the pump.
 6. The fuel supply system as claimed in claim 5 wherein said storage means comprise a capacitor and said draining means comprise a current sink.
 7. The fuel pump control circuit as claimed in claim 1 wherein said fuel pump control comprises: input means; electrical energy storage means responsive to said input means to store electrical energy; said input means adapted to receive the computing means output pulses and operative to cause said storage means to accumulate a maximum stored value during the receipt of the computing means output pulses; energy draining means connected to said energy storage means operative to dissipate the energy stored therein; and pump output means connected to said energy storage means and said energy draining means operative to communicate the instantaneous energy level appearing at said storage means to the pump.
 8. The fuel supply means as claimed in claim 4 wherein said fuel pump control means comprises: electrical energy storage means responsive to said input means to store electrical energy; said input means adapted to receive the computing means output pulses and operative to cause said storage means to accumulate a maximum stored value during receipt of the computing means output pulses; energy draining means connected to said energy storage means operative to dissipate the energy stored therein; and pump output means connected to said energy storage means and said energy draining means operative to communicate the instantaneous energy level appearing at said storage means to the pump. 